Dampening system for lithographic offset printing presses



June 28, 1966 E. o. STRUDWICK 3,257,940

DAMPENING SYSTEM FOR LITHOGRAPHIC OFFSET PRINTING PRESSES Filed Nov. 23, 1962 2 Sheets-Sheet 1 FIG. l.

INVENTOR. EDWARD O. STRUDWICK ATTORNEY June 28, 1966 DAMPENING SYSTEM FOR LITHOGRAPHIC OFFSET PRINTING PRESSES Filed NOV. 25, 1962 2 Sheets-Sheet 2 Z G F INVENTOR. EDWARD O. STRUDWICK AT ORN EY United States Patent Office Patented June 28, 1966 3,257,940 DAMPENING SYSTEM FUR LITHOGRAPHIC OFFSET PRINTING PRESSES Edward 0. Strudwick, Wiliiamstown, N.J.; Dorothy M.

Strudwiek, administratrix of said Edward 0. Strudwick,

deceased Filed Nov. 23, 1962, Ser. No. 239,729 1 Claim. (Cl. 101-148) rep ls the fountain solution while retaining the ink whereas the other or non-printing portions of the plate are provided with a chrome or other surfacing which has an afiinityfor the fountain solution which in turn repels the ink, the ink having a greasy or oily consistencythus resulting in only the form itself being inked. The fountain solution is conventionally applied to the plate cylinder through a series of rolls culminating in a roll covered with a dampened sock bearing against the plate cylinder as it rotates. Ink is next applied usually through an arrangement of three rolls at the end of a roll chain system leading from the ink supply and breaking down the ink to thin film condition for application to the plate cylinder. The inked form is then offset onto a rubber blanketed roll or cylinder fromwhich it is printed onto a paper web following a path about another roll or cylinder.

In the offset printing process as outlined above, proper control of the amount of fountain solution applied to or retained by the printing plate is essential to a high quality printed product. An excess amount of fountain solution on the plate will result in a spotty, washed out, low quality final printed product, while a deficient amount will result in pick up or retention of ink on portions of the plate not a part of the form to be reproduced with the obvious consequence of a defective final printed product. The conventional means of applying fountain solution, referred to above, involves considerable equipment with little control and with other disadvantages, and depends for any success it may have upon application of the correct amount of fountain solution. This invention, having for its primary objective the solution to this critical fountain solution control problem, contemplates an approach thereto different from that of the means heretofore knownrather than endeavoring to control precisely the amount of fountain solution applied to the plate, it concerns itself simply with initially applying at least an adequate amount and then carefully controlling the amount retained on the plate by removing the excess. Removal of such excess is accomplished by this invention through the application of suitable vacuum, whereby the fountain solution is readily removed from the printing area while the affinity of the non-printing area for the fountain solution prevents removal thereof from this portion of the plate. Utilization of vacuum means to effect removal of fountain solution remaining on the plate after inking is also within the contemplation of this invention in order to avoid excessive wetting of the paper web.

A further important advantage of this invention is the accomplishment of sharper line delineation as well as of greater definition in the final printed form, due to the fact that the vacuum as applied tends to take advantage of mutual attraction of droplets of fountain solution adjacent to each other but on differing surfaces one of which attracts and the other of which repels the fountain solution. 0

Another advantage of the invention is that it makes possible the retrieval of the excess fountain solution solution through simplified means, whether brush appli-.

cators, spray nozzles, or other. Of course any means of application of fountain solution in current use could be retained while still deriving the advantages of the vacuum means of this invention.

The invention and the manner of attaining its objectives, together with the foregoing advantages as well as others which will be evident, will be readily understood from a reading of the following specification, considered together with the accompanying drawings, in which:

FIGURE 1 is an elevation view partly in cross-section of a part of an offset printing press illustrating the invention and showing the printing plate, the plate cylinder, fountain solution application means, vacuum means, and inking rolls; and

FIGURE 2 is an alignment or stretched-out plan view showing the plate cylinder, fountain solution application means, and vacuum means of FIGURE 1.

In the embodiment of the invention illustrated herein, printing plate 10 bearing the form to be printed may be of metal with its printing portions comprising a surfacing such as copper which will repel the fountain solution while retaining the ink applied thereto and with its nonprinting portions comprising a surfacing such as chrome which will attract the fountain solution while repelling the ink. Plate 10 envelops the periphery of plate cylinder 11, being tightened and fastened thereabout by conventially .in the direction of its rotation as indicated in FIGURE 1, are first, brush applicator means 15 for applying fountain solution to printing plate 10, secondly.

vacuum means 16 for removing excess fountain solution from printing plate 10, thirdly, inking rolls 17, 18, and 19 for applying ink to.,printing plate 10, and finally, conventional offset cylinder 20. It is to be noted particularly that FIGURE 2 necessarily for clarity shows brush applicator means 15 on the opposite side of plate cylinder 11 from vacuum means 16. FIGURE 1 however depicts the true positional relationships of these means.

In brush applicator means 15, brush roll 21 is juxtaposed parallel to plate cylinder 11, being mounted in stand 14 so as to be rotatable independently of plate cylinder 11, through suitable drive means such as gearhead DC. motor 22, shown in block outline in FIGURE 2. Fountain solution vat 23 extending lengthwise of brush roll 21 is fixedly mounted to stand 14 beneath roll 21 so that i.

the brush of roll 21 will pass through the fountain solution contained in vat 23 as roll 21 rotates. Suitably juxtaposed parallel to brush roll 21 and adjustably mounted to stand 14 is segmented cylindrical rod 24 to which is attached blade 25 extending longitudinally thereof and extending radially therefrom sufficiently for the brush of roll 21 to wipe against blade 25 as roll 21 rotates, such head 26 extends lengthwise of the plate cylinder 11 and is connected by conventional tubular means 27 to a suitable vacuum pump, not shown. Conventional means for separation of .recovered fountain solution and filtering and return thereof to vat 23 for re-use, though not shown, may be readily incorporated in association with tubular means 27. Vacuum head 26 terminates proximately of plate cylinder 11 in orifice or nozzle 28, and is mounted so as to be positionally adjustable with respect to plate cylinder 11 through the medium of rectangular cross-sectioned mounting bar 29 which is assembled to stand 14. Inverted U-shaped mounting brackets 30 affixed to vacuum head 26 overlap mounting bar 29 with horizontal clearances 31 sufiicient to provide desired limits of vacuum head 26 positional adjustment with respect to plate cylinder 11, and manipulation of turn screws 32 extending through clearance holes 33 in brackets 30 and internally threaded holes 34 in mounting bar 29 accomplishes the desired positional setting. Mounting bar 29 is assembled to stand 14 so as to permit limited longitudinal vibration thereof through a displacement on the order of a small fraction of an inch with respect to stand 14. End 29a of mounting bar 29, comprising aclamp to prevent bar 29 from .rotating, is slidably mounted to the operating side 14:: of stand 14 through holes 35, and end 2% of mounting bar 29 is slidably mounted to the drive side 1412 of stand 14 through hole 36. Reciprocating piston motor 37 is affixed to drive side 14b of stand 14 by means of bracket 38, being threadably assembled to mounting bar 29 in axial alignment therewith, operation of motor 37 thereby providing vibratory motion of mounting bar 29 and of vacuum head 26 longitudinally of the face of plate cylinder 11. Selective adjustment of the amounts of vacuum applied across the face of plate cylinder 11 is achieved through the system of ports 39 in vacuum head 26 spaced longitudinally of plate cylinder 11, each of such ports 39 being provided with its independently operable 1 closure or valve 40.

Inking rolls 17, 18, and 19, next in sequential order about plate cylinder 11 in the direction of its rotation are rotatably mounted to bear against printing plate in its position about the periphery of plate cylinder 11, as shown in FIGURE 1. Ink in thin film condition suitable for application to the plate 10 may be provided to the inking rolls 17, 18, and 19 through a suitable ink-breale' down roll chain, not shown, leading from an ink supply reservoir or fountain.

Finally in sequential order about plate cylinder 11 in the direction of its rotation, offset cylinder 20, rotatably mounted, is provided with rubber blanket 41, enveloping and fastened about the cylinder. The form to be printed is offset onto this rubber blanketed cylinder 20 from plate 10 on plate cylinder 11, and finally printed onto paper web 42 travelling between offset cylinder 20 and impression cylinder 43. Multiple color printing can be. readily achieved through positioning additional offset cylinders aboutimpression cylinder 43, the form to be printed by each such additional offset cylinder being provided by an additional plate cylinder and facilities for applying fountain solution and inking, duplicating those already described as associated with plate cylinder 11. Printing simultaneously on both sides of paper web 42 can of course be achieved by replacing impression cylinder 43 with an additional offset cylinder and its associated facilities, again duplicating those already described as associated with plate cylinder 11.

Flexibility and adjustablility are important features of this invention. The amount of fountain solutionbeing applied to printing plate 10 can be varied to suit condi tions by adjusting the speed of motor 22 driving brush roll 21 as well as by adjusting angular positioning of blade 25 with respect to brush roll 21 through rotation of cylindrical rod 24. Optimum effectiveness of vacuum applied to plate 10 through vacuum head 26 may be achieved by selection of overall degree of vacuum applied to vacuum head 26 through tubular means 27, by positioning of vacuum head 26 relative to plate cylinder 11 through adjustment of turn screws 32 either for a selected constant clearance across the face of plate cylinder 11 or for a progressively greater clearance moving from one end of the cylinder to the other, and by selective adjustment of valves 49 to close, partially open, or fully open selected ones of ports 39 to achieve different degrees of vacuum at different positions across the face of cylinder 11. Optimum settings will vary depending upon the nature of the form to be reproduced, its tonal variations, solidity, etc. Longitudinal vibration of vacuum head 26 through operation of piston motor 37 may be utilized to increase effectiveness of the vacuum in removing moisture droplets from plate 10, tending to overcome surface tension or mutual attraction of the droplets to each other. Although not shown in the illustrated embodiment, the invention contemplates utilization when desired of a second vacuum head, positioned with respect to plate cylinder 11 in its direction of rotation between the last inking roll 19 and offset cylinder 20, for further application of vacuum to printing plate 10 after inking to remove remaining fountain solution from plate 10 before offsetting of the form to be printed onto rubber blanketed offset clyinder 20.

It should be noted that added advantages of the vacuum means of this invention include substantial reduction in the amount of dampness transferred from plate 10 through rubber blanket 41 onto the paper web 42, avoiding need of pre-conditioning the web for dimensional stability through pre-wetting and drying prior to printing. Vacuum head 26 may also be utilized to extract fountain solution accumulated in locking means 12 simply by positioning plate cylinder 11 so as to juxtapose the nozzle 28 of vacuum head 26 and locking means 12.

It should be understood that the present disclosure has been made only for the purpose of illustration of a preferred embodiment of this invention, that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention, and that the invention includes all modifications and equivalents which come within the scope of the appended claim.

I claim:

In an offset printing press, a stand, a plate cylinder rotatably mounted in said stand, a printing plate affixed about the periphery of said plate cylinder, brush applicator means for applying fountain solution to said printing plate, and vacuum means for removing excess fountain solution from said printingplate, said brush applicator means including a brush roll juxtaposed parallel to said plate cylinder and rotatably mounted in said stand, a fountain solution vat extending lengthwise of said brush roll and fixedly mounted to said stand beneath said brush roll so that said brush roll passes through the fountain solution vat as said brush roll rotates, a segmented cylindrical rod juxtaposed parallel to said brush roll and adjustably mounted to said stand, a blade attached to said rod and extending longitudinally thereof and extending radially therefrom so that said brush roll wipes against said blade as said brush roll rotates, and said vacuum means including a vacuum head having a nozzle extending longitudinally of said plate cylinder and positioned proximately thereof, an elongated mounting bar assembled to said stand with its longitudinal axis parallel to the longitudinal axis of the plate cylinder so as to maintain a constant distance between said longitudinal axes and so as to permit limited longitudinal displacement of said mounting bar relative to said stand, a plurality of U-shaped mounting brackets affixed to said vacuum head, turn screws assembling said U-shaped mounting brackets to said mounting bar so that adjustment of said turn screws displaces said vacuum head relative to said mounting bar so as to vary the clearance between the vacuum head nozzle and the printing plate, and drive means assembled to said mounting bar so as to provide longitudinal vibratory movement of said mounting bar relative to said stand and of said vacuum head nozzle relative to said printing plate, said vacuum head having a plurality of ports therein and an independently operable valve for each port, a vacuum pump, and tubular means connecting said vacuum head to said vacuum pump.

UNITED References Cited by the Examiner STATES PATENTS 2/1952 Dunphy 15-306.1 X 3/1952 Bassist 101142 2/1956 Mullen 101-147 10/ 1958 Pritchard 101147 1/1959 Dahlgren 101147 11/1960 Doyle 101-416 FOREIGN PATENTS 7/1932 France. 4/ 1960 France.

ROBERT E. PULFREY, Primary Examiner.

R. H. BERNEIKE, JULIUS R. FISHER,

Assistant Examiners. 

